1. Technical Field
The present invention relates to a method of driving an electrophoretic display device, an electrophoretic display device, and an electronic apparatus.
2. Related Art
In electrophoretic display devices of this type, an image is displayed by applying an electric potential difference between a pixel electrode and a common electrode that face each other with electrophoretic elements including electrophoretic particles interposed therebetween so as to move the electrophoretic particles (for example, see 2002-116733). In addition, the electrophoretic display devices of this type have a memory characteristic for conserving a displayed image even in a state that no electric potential difference is applied between the pixel electrode and the common electrode.
In addition, the electrophoretic display devices of this type can display images each having three gray scale levels or more. For example, in a case where the electrophoretic display device has the electrophoretic element including a plurality of white particles and a plurality of black particles that are charged with different charges as the electrophoretic particles, first, an electric potential difference is applied between the pixel electrodes and the common electrodes for representing a whole black display (that is, the black particles are attracted to the common electrodes of all the pixels, and the white particles are attracted to the pixel electrodes of all the pixels). Then, by applying an electric potential difference between the pixel electrode and the common electrode such that the black particles are attracted to the pixel electrode side and the white particles are attracted to the common electrode side only for a time period corresponding to the gray scale level of each pixel, a gray image can be displayed.
However, in the electrophoretic display devices of this type, when a predetermined time elapses after the image is displayed, a part of the electrophoretic particles collected in each electrode diffuses. Accordingly, for example, the reflectance of a part, which is to be displayed in a white color by the white particles, of the displayed image may decrease, and the reflectance of a part, which is to be displayed in a black color by the black particles, of the displayed image may increase. Therefore, there is a problem that the contrast of the displayed image may decrease. Accordingly, for example, in JP-A-3-213827, in order to improve the decreased contrast, technology for performing a refresh operation at each interval of 10 minutes to several tens of hours has been disclosed.
The above-described refresh operation is an operation for improving the contrast that has decreased due to diffusion of a part of the electrophoretic particles at a time when ten minutes or more elapses from display of the image. However, additionally, inventors of the invention and the like found a kickback phenomenon in which the contrast decreases in several seconds right after the image is displayed (that is, right after the image is written). Thus, for example, in the above-described case where an image having three gray scale levels or more is displayed by initially applying an electric potential difference between the pixel electrodes and the common electrodes for displaying the whole black display, and then, by applying electric potentials between the pixel electrodes and the common electrodes in accordance with the gray scale levels of the pixels, a technical problem that the contrast may decrease due to the kickback phenomenon in addition to the decrease in the contrast due to the diffusion of a part of the electrophoretic particles may occur.